amdgpu: Corrupted video on 32 bit systems (possible fix)

[Nils Holland]

On Fri, Jan 20, 2017 at 11:47:53AM +0900, Michel Dänzer wrote:
> On 20/01/17 04:35 AM, Nils Holland wrote:
> > 
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c	2016-12-11 20:17:54.000000000 +0100
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c	2017-01-19 15:38:56.972034489 +0100
> > @@ -372,6 +372,10 @@
> >  	if (!drm_arch_can_wc_memory())
> >  		bo->flags &= ~AMDGPU_GEM_CREATE_CPU_GTT_USWC;
> >  
> > +	#ifdef CONFIG_X86_32
> > +		bo->flags &= ~AMDGPU_GEM_CREATE_CPU_GTT_USWC;
> > +	#endif
> > +
> >  	amdgpu_fill_placement_to_bo(bo, placement);
> >  	/* Kernel allocation are uninterruptible */
> >  	r = ttm_bo_init(&adev->mman.bdev, &bo->tbo, size, type,
> 
> The corresponding code in the radeon driver has changed quite a bit
> since this original fix. It would be better to bring the amdgpu code in
> line with the current radeon code.
> 
> 
> > With this patch, the amdgpu driver works fine for me on my 32 bit
> > kernel: All graphics output looks the way it's supposed to, even with
> > full acceleration enabled - great!
> > 
> > I'd suggest that it might be a good idea to put to apply the above
> > patch or something similar to the official sources.
> 
> Indeed. Do you want to create a proper patch and submit it to the
> amd-gfx mailing list for review? See Documentation/SubmittingPatches for
> more information.

Sounds like a good idea! I was a bit heasitant because, to be honest,
I'm not at all an expert about the code in question and basically only
saw how you fixed the issue in radeon and thought: "Well, let's see if
I can do the same thing in amdgpu and if so, if it helps there, too".
;-)

However, since you've said that a 32 bit fix in amdgpu generally seems
like a good idea, I would indeed use a little time on the weekend to
get a proper patch ready and submit it for review. Even if the "no wc
for x86_32" part is probably the only thing it'll contain - more of
"bringing the amdgpu code in line with the current radeon code" might,
for the time being, be beyond my capabilities, at least if we assume
that the code should stay in a sane and working condition. ;-)

Thanks and greetings
Nils